Fluid pressure regulator



March 9, 1937. R. B. LEWIS FLUID PRESSURE REGULATOR Original Filed Oct. 12, 1932 INVENTOR %(AT1:ORNEY F050? 75. Law/s Patented Mar. 9, 1937 FLUID rrmssuan amum'ron Robert B. Lewis, Philadelphia, Pa, aslignor to Tinius Olsen Testing Machine Company, Philadelphia, Pa., a corporation of Pennsylvania Original application October 12, 1932, Serial No.

637,394. Divided and this application Septembe! 26, 1933, Serial No. 690,993

2Claims.

The present invention relates to control valves for testing machines and more particularly to a valve for maintaining a uniform rate of loading for a testing machine by a fluid under pres- I sure.

This application is a division or applicant's co -pending application, Serial No. 637,394, filed October 12, 1932, for Universal testing machine.

Some of the objects of the present invention 10 are to pr'ovide an improved control valve for maintaining a uniform rate of travel of a movable part actuated by fluid under pressure; to provide a control valve for insuring a constant rate of loading for a testing machine or other is apparatus dependent for operation upon fluid pressure; to provide a control valve having different eirective areas so that there is a diflerential action of the valve in operation which functions as a control to maintain a constant rate of 2 loading by the pressure fluid: to provide a valve for use in hydraulic systems wherein there is normally an increase of pressure as the load is applied and which valve operates to build up a pressure at some predetermined established rate;

25 to provide a valve operating through a differential ,action in such a manner as to obtain high pressures at a faster rate than heretofore and which rate is dependent upon the rate of difl'erential action; to provide a novel valve mechanism 30 for regulating the flow from a pump; and to provide other improvements as will hereinafter appear. Y

In the accompanying drawing Fig. 1 represents a side elevation of a portion of a hydraulic oper- 35 ated testing machine broken away to show the control valve which embodies one form of the present invention; Fig. 2 represents on a larger scale a longitudinal section of the control valve in association with its piping to the pressure fluid 4 supply and the cylinder of a testing machine;

and Fig. 3 represents diagrammatically the assembled association oi the regulator.

Referring to the drawing one form of the present invention consists of a valve casing l ar- 45 ranged to communicate at one end with the discharge. pipe II or a'pump I2 and at the other end by a pipe l3 with a pressure fluid supply pipe ll leading to a load applying device such as the movable cylinder ii of a hydraulic operated 50 testing machine. In the machine to which the present invention is applied as an example of its use the conduit I4 is in communication with a port it which extends longitudinally of a fixed piston member l1 and opens against the head of 55 the cylinder I5 to cause the latter to move relative thereto under the applied pressure of the actuating fluid. As' here shown the cylinder is slidably mounted upon the piston I! and its flanged head I8 is guided upon two lead screws I! which extend in opposite directions therefrom, the upper ends thereof being guided through the flxed piston for bolting engagement with a crosshead 20 to which the test piece is arranged to be secured for testing purposes as well known in this type of apparatus. Preferably the head 18 seats on the hubs of the two spur gears 2| which are threaded upon the lead screws l8, while a yoke 22 bears against the opposite hubs of the gears 2|. A spring 23 is coiled about a rod 24 and reacts against a flxed abutment 28 to hold the yoke 22 pressed upwardly whereby the cross "in a T-fltting 30 having branches leading through regulating valves SI and 32 to the pipes I3 and I4. For controlling the pressure fluid to 30 maintain a selected rate or loading, the casing I8 is provided with two coaxially located bores 34 and 38, the former, for more definite identification, being called the pressure supply bore 84 and 'the latter the back pressure bore :0. It should however be particularly noted that the diameter of the bore 88 is greater than that of the bore 38 in order to give the novel diflerential action desired. Pressure fluid is led to the back pressure bore 35 by the pipe I! where it acts against a piston 38 to vary the response of a check valve 31 to pressure from the pump discharge pipe II. A valve stem 38 interconnects the piston 38 and the check valve 31 and has a bearing in the-body Ill between the bore 38 and'a chamber 40, the latter being in communication with the bore 84 when the check valve 3'! is open. A coil spring I encircles the stem 38 and is adjusted to give a predetermined closing pressure to the check valve 31, and this adjustment ccmprehends a pressure to maintain the valve 8! closed as long as the rate of flow through the pipe 28 is uniform. Any change or such rate is followed by a building up of the pressure in the discharge line from the pump, and will thus cause the so valve 31 to open and by-pass all or a part of the discharge by way of a return pipe 42 whichleads from the chamber to the fluid supply reservoir. In order to adjust for a predetermined rate of flow either the regulating valve 3! or 32 is initially opened or both opened sufficiently to adjust for the desired predetermined rate of flow of liquid to the pipe II. It is the diflerence in pressure between opposite sides of the valves 3| or 32 which determines the amount of liquid passing the opening in the opened valve as will be understood. It is this regulated flow of -liquid under pressure through the pipe M which causes the cylinder 15 to move and place the cross-head or yoke 20 under load. As the loading pressure increases the back pressure reacts through the fluid and by way of the pipe I3 upon the piston 36. This back pressure holds the valve 31 in the closed position until the pump builds up enough pressure to overcome it, which, because of the fact that the piston 36 is larger in cross sectional area than the valve 31, must be greater than the back pressure by a certain flxed proportion. The result is that when the pump is in operation and the valves are partly open, the pressure between the pump and the valves is always greater by a fixed proportion than the pressure between the valves and the cross-head. Although the actual quantitative difference in pressure becomes greater as the pressure on the whole system increases, the difference in pre'- sure is still proportioned to the pressure on the system and increases in quantity only with sufficient rapidity to compensate for the increased leakage and increased resistance to flow in the system. Thus, the result is a uniform rate of loading for the testing machine.

In the operation of the pressure control of the present invention the spring 4| is initially set for no load conditions in the flow of fluid from the pump H. To regulate the loading pressure and establish a predetermined rate of loading either or both the regulating valves 3| and 32 is opened until the desired rate is established. With this rate fixed and the cross-head 20 moving under the applied load any increase in back pressure is transmitted by the pipes i4 and [3 to the piston 86 thereby increasing the pressure on the by pass valve 31 above the pressure exerted by the preloading spring 4!. This combined effect proportionately increases the closing effort so that a difierence in pressure is maintained between the bore 34 and the chamber II which is variable in a manner depending upon the operating pressure. If for any reason it is desired to increase the rate of loading without changing the set condition of the opened valve either 3! or 32, the other valve can be opened, but when the latter is again closed the predetermined or set rate of flow is resumed.

While only a single form is shown in which this invention may be embodied, it is to be understood that the invention is not limited to any specific construction, but might be applied to various forms without departing from the spirit of the invention or the scope of the appended claims.

Having thus described my invention, I

claim:--

l. A control mechanism comprising the combination of a pump, a load applying mechanism, a conduit for pressure fluid leading from said pump to said load mechanism, a control valve in said conduit for adjusting the rate of flow therethrough, a casing having a conduit forming a by-pass for fluid discharged from said pump, a spring actuated check valve for controlling said by-pass, a piston having an operating area greater than the like area of said check valve,-

means to transmit movement of said piston to said check valve to supplement the action of said spring, and means including a pipe for subjectingsaid piston to the back pressure from said loading mechanism.

2. A system for supplying fluid against an increasing head at an adjustable rate that comprises a fluid pump, a throttle valve through which the fluid passes from the pump to the point at which it is to be supplied, a surface exposed to the pressure of the fluid on each side of the throttle valve, the surface between the pump and the throttle being slightly smaller than the surface on the other side of the throttle, and a valve for by-passing fluid from the pump. said valve being connected for operation to the two surfaces in such a manner that the valve will open when the pressure between the pump and the throttle exceeds that beyond the throttle by a pre-determined proportion.

ROBERT E. LEWIS. 

